1. Field of the Invention
The present invention relates generally to clutches, particularly for motor vehicles, and refers more particularly to clutches of this kind which are operated by fluid pressure, e.g. hydraulically.
2. Description of the Prior Art
Generally speaking, a clutch comprises at least one clutch assembly comprising a reaction plate intended to be rotationally fixed to a first shaft, generally a drive shaft, a friction disc which is movable axially in relation to the reaction plate and is intended to be rotationally fixed on a second shaft, generally a driven shaft, a pressure plate axially movable in relation to the reaction plate and rotationally fixed on the latter, elastic means which urge the pressure plate in the direction of the reaction plate in order to clamp the friction disc, and at least one pivoting clutch release lever adapted to effect the release of the friction disc.
The element necessary for operating the clutch release lever or levers is generally known as the clutch release thrust bearing and is operated either mechanically or hydraulically by a clutch release pedal.
In the case of a mechanically operated clutch release thrust bearing, the efficiency ratio between the force applied to the clutch release pedal and the force axially transmitted to the thrust bearing by the mechanical linkage interposed between the latter and the pedal is relatively poor due to the play and flexibility inevitably present in a mechanical linkage of this kind. In addition, because of this play and flexibility and also because the clutch release thrust bearing is not generally held in contact with the clutch release lever or levers, the response of a mechanically operated clutch release thrust bearing of this kind is not immediate, and the backlash or idle travel of the pedal operating it must be frequently adjusted.
Hydraulically operated clutch release thrust bearings do not have these disadvantages, and in particular they have good efficiency; however, up to the present time hydraulically operated clutch release thrust bearings have been located in a circular continuous casing engaged axially on the shaft connecting the clutch to the gearbox.
In consequence, the slightest operating incident, for example the slightest leakage, makes it necessary for a hydraulically operated clutch release bearing of this kind to be removed for repair or replacement; in order to effect this removal, it is necessary to disconnect the clutch from the gearbox, and this very substantial dismantling operation is lengthy, complex, and expensive.
The main object of the present invention is to provide an arrangement which enables this disadvantage to be overcome.